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Rotational Motion of a Rigid Body: Moment of Inertia — Important Questions

ICSE · Class 11 · Physics

51 important questions from Rotational Motion of a Rigid Body: Moment of Inertia for ICSE Class 11 Physics, with answers.

51 questions38 flashcards18 formulas & key relations5 concepts

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A 3D diagram illustrating the definition of torque (τ = r x F). It shows a force vector (F) applied at a point with position vector (r) relative to an origin, and the resulting torque vector (τ) perpe
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multiple choicemultiple correct

Important Questions from Rotational Motion of a Rigid Body: Moment of Inertia

1multiple choice
3 marks

A body has angular momentum 24 kg m²/s and moment of inertia 8.0 kg m². If the angular momentum remains constant and the moment of inertia becomes 6.0 kg m², what is the new angular velocity?

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4.0 rad/s

Since L = Iω remains constant, first confirm L = 24 kg m²/s. For the new situation, ω = L/I = 24/6.0 = 4.0 rad/s.

2multiple choice
3 marks

A ring of mass 4.0 kg and radius 0.50 m rotates about its central axis perpendicular to its plane with angular velocity 10 rad/s. What is its rotational kinetic energy?

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50 J

For a ring about its central axis, I = MR² = 4.0 × 0.50² = 4.0 × 0.25 = 1.0 kg m². Then K = 1/2 Iω² = 1/2 × 1.0 × 10² = 50 J.

3multiple choice
3 marks

A rigid body has moment of inertia 9.0 kg m² and rotational kinetic energy 72 J. What is its angular velocity?

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4.0 rad/s

Use K = 1/2 Iω². So 72 = 1/2 × 9.0 × ω² = 4.5ω². Hence ω² = 16 and ω = 4.0 rad/s.

4multiple choice
3 marks

A body with angular momentum 30 kg m²/s has its moment of inertia reduced from 10 kg m² to 6.0 kg m² without external torque. What is the ratio of the final angular velocity to the initial angular velocity?

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5/3

With no external torque, Iω is constant. So I₁ω₁ = I₂ω₂. Therefore ω₂/ω₁ = I₁/I₂ = 10/6 = 5/3.

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What are the important topics in Rotational Motion of a Rigid Body: Moment of Inertia for ICSE Class 11 Physics?
Key topics in Rotational Motion of a Rigid Body: Moment of Inertia include Torque and Angular Momentum, Rigid Body, Motion Variables, and Equations of Rotational Motion, Moment of Inertia and Radius of Gyration, Theorems of Parallel and Perpendicular Axes. Study these first, then practise questions on each for Class 11 exams.
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Super Tutor has 51 practice questions for Rotational Motion of a Rigid Body: Moment of Inertia, including multiple choice, multiple correct questions. A sample with answers is on this page.

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